In U.S. Pat. No. 3,472,765 use of a membrane separation device in a biological reactor is described for removing one or more constituents from a fluid mixture by passing a fluid mixture through a selectively permeable fluid separation medium that is a component of the separation device. Fluid membrane devices include membrane modules that generally fall under three membrane categories: tubular, hollow fiber, and flat sheet porous membranes. Techniques described in the art that are suitable for manufacturing membrane modules are disclosed in U.S. Pat. No. 6,284,137-B1, U.S. Pat. No. 4,230,463, and U.S. Pat. No. 3,615,024.
Flat sheet porous membranes that are included as part of plate-and-frame modules along with hollow fiber membrane modules are membrane types used to process water and wastewater. Porous hollow fiber membrane modules and methods of making them are described in European Patent Publication 1,166,859-A2, U.S. Pat. App. 2002/0011443-A1, U.S. Pat. No. 4,440,641; U.S. Pat. No. 4,886,601; U.S. Pat. No. 6,325,928; U.S. Pat. No. 5,783,083; U.S. Pat. No. 5,639,373, U.S. Pat. No. 5,248,424, U.S. Pat. No. 5,922,201, and U.S. Pat. No. 5,914,039.
Flat sheet porous membrane modules are described in U.S. Pat. No. 5,651,889, and European Pat. Publication 1,127,849-A1. Flat sheet porous membrane modules can be assembled in pleated cartridges, spirally-wound modules, or plate-and-frame configurations. Plate-and-frame flat sheet membrane modules are typically easier to clean than other types of membrane modules.
Support layers may be used to keep a space between two flat-sheet membranes to provide for conveyance of fluid to or from the space between the membranes via a manifold connected to the flat-sheet membrane modules. Support layers may be in the form of a permeable mesh designed to keep the membrane module from collapsing under any internal vacuum or external pressure. Alternatively, support layers can be in the form of a paper mesh, a non-woven or a woven-fiber based material. Some examples of support layers are disclosed in U.S. Pat. No. 4,701,234, U.S. Pat. Nos. 3,679,059, 4,871,456, 4,264,447, and European Pat. No. 0,602,560-B1.
Plate-and-frame module designs may include a support plate rather than a support mesh to provide strength and rigidity to membrane modules. European Pat. No. 0,602,560-B1 discloses a structured support plate that contains a mesh of grooves cut into the support plate to enhance fluid transfer. U.S. Pat. No. 5,626,751 describes a module support plate made of metal. Other support plate designs are found in U.S. Pat. No. 5,482,625 and PCT Publication WO 99/65595.
Attachment of the support layer to the membrane layer can be accomplished by an adhesive, such as disclosed in U.S. Pat. No. 5,071,553, European Pat. No. 0,653,240-A1, U.S. Pat. No. 5,772,831, or by melting the membrane, the support plate or both using thermal fusion or ultrasonic waves, such as disclosed in European Pat. No. 0,602,560-B1, U.S. Pat. No. 5,482,625, U.S. Pat. No. 5,651,888, U.S. Pat. No. 4,701,234, U.S. Pat. No. 6,287,467-B1, U.S. Pat. No. 4,264,447, and U.S. Pat. No. 4,302,270.